TEE COURSE OF NATURE. 



489 



of thought which I have before indicated. All 

 are agreed that the course of Nature is deter- 

 mined by what we may call causes or laws ; but 

 all are not agreed as to the scope of action of 

 these laws. The great and distinguishing feat- 

 ure which the school of science recognizes, and 

 which the other school does not recognize, is that 

 all the laws of Nature act without any scrutable 

 regard to consequences. I qualify my statement 

 by the word scrutable because it is entirely out- 

 side the pale of scientific thought to speculate 

 upon possible inscrutable ends in Nature. This 

 being a subject on which the man of science, 

 speaking as such, can affirm nothing, so he can 

 deny nothing. Having found that no trace of 

 regard for consequence can be seen in the mode 

 of action of the laws which he investigates, but 

 that the whole course of things, so far as his eye 

 can penetrate, may be explained and predicted 

 without supposing any such regard, the demands 

 of science are satisfied, and he must there stop. 



Let me illustrate this by going over the train 

 of thought which has just occupied us in the op- 

 posite direction, starting from the rainfall and 

 tracing the succession of causes to the fall of the 

 rock. The spot at which each drop of rain shall 

 fall is determined by antecedent conditions en- 

 tirely — by gravitation and the winds. The drop 

 neither seeks nor avoids the crevices ; never asks 

 in any way what shall be its destiny after it reach- 

 es the ground. It strikes the ground wherever 

 gravity and the winds bring it, percolates through 

 the soil according to the law of least resistance, 

 and dissolves the rock according to the laws of 

 chemical affinity, without any regard to the con- 

 sequences, immediate or remote. At length a mo- 

 ment arrives at which the cohesive force of the 

 rock becomes less than the weight which urges 

 it downward. This moment is fixed entirely by 

 antecedent circumstances, such as the solubility of 

 the rock and the amount of water which perco- 

 lates over it. At that very moment the rock be- 

 gins to fall. It falls sixteen feet the first second, 

 three times that distance the next, and so on, ac- 

 cording to the mathematical law of falling bodies, 

 without any respect to the lovely character of the 

 beings it may destroy, or the disasters with which 

 it may crush the fondest hopes of men. The re- 

 gion may be the wilderness ; the passer-by may 

 be a babe in its nurse's arms ; an angel of chari- 

 ty, fulfilling her mission of good- will ; or a mur- 

 derer, aiming the deadly blow at his victim : but 

 under no circumstances can we see that these 

 conditions in any way affect the chain of causes 

 which lead to the falling of the rock, or cause it 



to wait a moment, or swerve a hair's breadth 

 from its inevitable course. 



According to the theory of the course of Na- 

 ture which I am trying to elucidate, the chain 

 of causes which we have described, each cause , 

 acting according to antecedent conditions, but 

 without any regard to consequences, is the type 

 of the whole course of inanimate Nature, as far 

 in space as the telescope can penetrate, and as 

 far back in time as the geological record can be 

 deciphered. An essential feature of the theory 

 is, that the laws which connect the several links 

 of the chain, and thus determine the progress of 

 events, do not possess that character of inscruta- 

 bility which belongs to the decrees of Providence ; 

 but are capable, so for as their sensible manifes- 

 tations are concerned, of being completely grasped 

 by the human intellect, and expressed in scientific 

 language. Without this the theory would have 

 no practical bearing whatever ; because, to say 

 that the course of events is fixed, but by laws 

 which we can never grasp, would give us no 

 clew at all to learning what that course shall be, 

 and would be equivalent to telling us that it is 

 enshrouded in the same impenetrable mystery 

 with first causes. A very important feature of 

 the progress of science is found in the constant 

 resolution of the laws of Nature into more simple 

 and elementary ones, until we reach principles so 

 simple that it is impossible to analyze them fur- 

 ther. Let us take, as an instance of this, the 

 laws of the celestial motions. When Kepler dis- 

 covered that the planets moved round the sun in 

 ellipses, having the sun in one focus, he found 

 what were for his time simple and elementary 

 laws. They were entirely comprehensible, ad- 

 mitting of being expressed in mathematical lan- 

 guage. They enabled him to predict the motions 

 of the planets, and, so far as the intellect of the 

 time could penetrate, they could not be resolved 

 into more simple expressions. 



But when Newton appeared on the scene, he 

 showed that these and other laws could be ex- 

 pressed in the simple and comprehensive form 

 of gravitation of every particle of matter toward 

 every other particle with a force inversely as the 

 square of the distance which separates them. All 

 the laws of planetary motion which had before 

 been discovered were shown to be reducible to 

 this one simple law, combined with certain facts 

 respecting the directions and velocity of the plan- 

 etary motions. The most essential of these facts 

 is, that the velocities of the planets in their orbits 

 are such that their orbits, under the influence of 

 the sun's gravitation, are nearly circular. 



